Ubuntu: How do i take a disk image of Ubuntu 16.04 on a NAS

Question:

I have recently installed Ubuntu 16.04 in a VM running on a Windows 10 host. As a complete newcomer to Linux, never mind Ubuntu, I am completely baffled by the setting up of a simple backup of the disk to a share on a network attached Drobo. I have looked at 'bacula' and the complexities and apparent insistence of using Tape astound me.

I want to set up a backup which can be started manually to take an image of the Ubuntu disk and store it on a share in my Drobo. I also want to test that I can recover the image to the main disk of the Ubuntu system.

The backup should be an Incremental or Differential type. I note that there is apparently no known software that does Differential backups.